I'm about a month away from my PhD defense, and my goal is to work in industry (I'm in medicinal chemistry and I've been doing high-throughput screen and in vitro inhibition assays of a particular enzyme). I started job searching in industry about a month ago, thinking that I shouldn't have problems finding suitable positions. However, as I've started searching and applying, I've noticed that a lot of the jobs in biopharma that are posted require things like mammalian cell culture work, transfection, genomics, immunology etc., which I don't have experience in. Therefore, I'm thinking that I may need to do a postdoc after all to gain experience in those areas - there's some very important skills that I'm apparently missing! Of course, if I get an industry offer, I'll go ahead and take it, but it seems like I may not be qualified for PhD-level positions (I'm open to taking a MS-level position but most employers would consider me "overqualified"). But it's a month before my defense and it's rather late in the game when it comes to postdoc apps. My advisor can only fund me for another 2.5 months (end of June). How much trouble am I in in terms of getting a postdoc that is rather significantly different from my PhD? How long of a gap is acceptable to potential postdoc PIs?
I started job searching in industry about a month ago
I am not familiar with your individual situation, but for any job search I would recommend allowing a minimum of three months. If you expected to find a job within one month then you would be in very bad trouble. Keep in mind that a job application often waits a month to be read and a job offer often takes a month to be approved by an employer.
The content of a job ad is not an accurate predictor of the qualifications of the person who is hired.
Look up the profiles of people who have the job you want. That will get you data, as opposed to opinions.
How much trouble are you in: that really depends on what country you are looking for postdocs in. Positions open up at different times in different regions. For me, the academic year starts in September, so there are lots of postdoc positions being posted now.
However, if you want to work an industry job, then you are far better off just applying for them. Your skills are transferable, and what you don't know you will learn on the job. Your ability to learn quickly is more important than what you have already learned, especially when you are going to be applying for more junior positions anyway.
Don't be intimidated. Just go for it and most importantly, be open to change.